Nitrogen monoxide composition for use as a drug

ABSTRACT

The invention relates to a method for the treatment or prevention of hypoperfusions of abdominal organs comprising administering a gaseous medication containing nitrogen monoxide and carbon dioxide to the patient. The gaseous medication is administered by the intra-abdominal route.

This invention relates to the use of a stable gaseous compound on a baseof nitrogen monoxide (NO) and carbon dioxide (CO₂) to produce a gaseousmedication intended for the treatment or prevention, by theintra-abdominal route, of hypoperfusion of the abdominal organs, inparticular, in the case of a procedure involving laparoscopy orlaparosurgery.

Nitrogen monoxide is produced naturally in mammals by an enzyme, calledNO-synthase, which is expressed in terms of its makeup by theendothelial cells, by the platelets, and by the central and peripheralnervous systems. Another form of calcium-independent NO-synthase can beinduced by different stimuli (especially liposaccharides) in numerouscells, such as macrophages, lymphocytes, myocardial cells, endothelialcells, and the smooth muscular cells.

Nitrogen monoxide is an important biological messenger in mammals, andthis molecule plays a decisive role in the local control ofhemodynamics.

It has been possible to make evident the release of NO by means of theendothelial cells in the case of variations in the blood flow. Nitrogenmonoxide appears especially as a major component of the physiologicaladaptation of the vascular diameter to blood perfusion: reactivehyperemia is thus attenuated in a most noticeable fashion on thecoronary level. Conversely, a chronic increase in the blood flow,produced by an arteriovenous fistula, increases the dependentrelaxations of the endothelium.

The capacity of nitrogen monoxide, produced at the level of the vascularwall and in the neighboring tissues, to regulate precisely the vasculartonus by adaptation of the blood flow is remarkable. Likewise, it hasbeen assumed that the NO that is released during neuronal activity couldregulate the tonus of cerebral microcirculation, thus linking theactivity and the cerebral blood flow. We also recall the role played byNO in the regulation of the proliferation of smooth vascular musclewhich is a decisive factor in vascular compliance.

Nitrogen monoxide furthermore controls the post-capillar venularpermeability.

Nitrogen monoxide also participates in hormonal regulation mechanisms atthe level of the kidney by inhibiting the release of renin, and on thecardiovascular level by opposing the release of the natriuretic factor(ANF).

Finally, in vivo, platelet activation is under the permanent control ofendothelial nitrogen monoxide and, to a lesser degree, it is under thecontrol of platelet NO-synthase itself. During aggregation, theplatelets release nucleotides (ATP, ADP), serotonin, PAF, thromboxaneA2, and vasopressin; they can also initiate the gush of coagulation byreleasing thrombin. In response to ATP, ADP, serotonin, PAF, andthrombin, the endothelial cells release NO and prostacyclin, both ofwhich act together to prevent and counter the process of plateletaggregation.

The abnormal decline in the nitrogen monoxide rate, observed in the caseof numerous diseases, seems to confirm the importance of its role in theorganism. Such a decline is characteristic of hypertension,hypercholesterolemia, atherosclerosis, and diabetes.

Likewise, a very early reduction of the basal release of NO would be thecause of problems related to the re-perfusion of ischemic areas, such ascoronary thrombosis and vasospasms.

Various vasodilator agents have been developed so far on the basis ofthese findings. These substances, known as nitrovasodilators, produce NOin vivo and thus make up for a deficiency in the endogenous NO. By wayof example, one might mention molsidomine or sodium nitroprussiate,which make it possible to prevent the phenomena of platelet adhesion andaggregation.

To make up for insufficient production of NO, there has even been aproposal for the administration of L-arginine or analogues ofL-arginine, since L-arginine intervenes directly in the biosynthesis ofnitrogen monoxide as a substrate of NO-synthase.

In view of the significant contribution made by nitrogen monoxide to themaintenance of a low pulmonary circulation pressure and the importanceof the resultant local vasodilator effect, it has also been suggestedthat NO be directly administered by way of inhalation in the treatmentof acute pulmonary arterial hypertension. The extensive research donealong these lines demonstrated the therapeutic effectiveness of agaseous mixture of nitrogen monoxide and inhaled nitrogen at dosesbetween 1 and 20 ppm of NO on patients suffering acute respiratorydisorders: in fact, a reduction of pulmonary arterial hypertension,possibly accompanied by an improvement of the ventilation-perfusionratios due to an intrapulmonary shunt, was observed.

Surgical procedures involving laparoscopy are being practicedincreasingly because, compared to conventional techniques involving openlaparotomies, they make it possible to reduce not only the duration ofhospitalization but also the scar formation time and, by the same token,post-operative pain.

However, although this technique of laparoscopy offers numerousadvantages, it also entails one major inconvenience.

In effect, the technique of laparoscopy is usually accompanied by aninsufflation of the abdomen (intra- or extra- peritoneal insulation) ofa gas, such as CO₂, which insufflation causes an increase in thepressure being exerted inside the abdomen.

This increase in intra-abdominal pressure results in a decrease--harmfulto the patient--of the blood flow of the abdominal organs, inparticular, the kidneys and the intestines, and a disorder of thefunctions associated with these abdominal organs, such as diuresis andintestinal transit.

These disturbances are essentially due to a phenomenon of hypoperfusionof these organs, tied to the pressure increase due to insufflation; theyare all the more harmful to the patient than the length of theprocedure, in other words, the surgical operation, is important.

The object of this invention thus is to mitigate the above-describedproblems.

The invention thus relates to the use of a gaseous compound, containingnitrogen monoxide (NO) and carbon dioxide (CO₂), to produce a gaseousmedication intended for the treatment or the prevention, by theintra-peritoneal route, of hypoperfusions of the abdominal organs.

By intra-abdominal route, we mean the intra-peritoneal orextra-peritoneal route.

The NO/CO₂ medication mixture of the invention is particularly suitablefor the administration by intra-abdominal insufflation during aprocedure involving laparoscopy or laparosurgery; the peritoneum hererefers to the serous membrane that lines the abdominal cavity.

The gaseous medication of the invention is preferably made up of asingle mixture of carbon dioxide and nitrogen monoxide; however, theaddition of at least one gas chosen from the group made up of xenon,krypton, nitrogen protoxide and their mixtures, to said mixture of CO₂and NO, can also be considered.

The concentration of NO in the gaseous mixture of NO+CO₂ is an effectiveconcentration, preferably between 1 and 100 ppm. A concentration of lessthan 1 ppm is not desirable and a concentration of more than 100 ppmleads to a progressive disappearance of the therapeutic effect. Thereasons for the low activity level observed in such concentrations areas yet unknown, but could be related to a local toxicity or possibly thesaturation of the nitrogen monoxide receptors.

According to a preferred embodiment, the concentration of NO in themedication mixture is between 15 and 30 ppm.

The stability of the gaseous medication in this invention makes itpossible to store it under pressure under conventional conditions inbottles made of steel or a light alloy on a base of aluminum.

To prevent any risk of contamination, bottles made of a light alloy on abase of aluminum are preferred. The preferred storage conditions thatensure stability in excess of 2 years are a temperature between 15 and30° C., preferably between 20 and 25° C., and a pressure between 20 and30 bar.

The compounds of the invention can be administered by means ofintra-abdominal insufflation and, more particularly, by intra-peritonealinsufflation. To do that, we proceed in the known manner. Afterabdominal incision, the NO/CO₂ compound is insufflated into theabdominal cavity by means of a needle that is connected to aninsufflator, such as the insufflator of the MP video type Medicam 900.Throughout the procedure, an internal pressure of between 10 and 20 mmHg is maintained in the abdominal cavity. We note that the insulation ofthe mixture of CO₂ and nitrogen monoxide is neither described norsuggested in the literature. The vasodilating and plateletanti-aggregating activity of NO is particularly suitable for thetreatment of side effects linked to a decline in vascular blood flow tothe intra-abdominal organs during procedures involving laparoscopy.

The quantity of medication compound to be administered, however, dependson the age of the patient, the seriousness of the ailment from which hesuffers, and the NO concentration of the injected gaseous compound.

Examples 1 to 2 below, illustrate the stability of the compounds of theinvention, as well as their therapeutic usefulness.

EXAMPLE 1

Various mixtures of nitrogen monoxide and carbon dioxide were preparedand packaged in bottles of type B5, consisting of a light alloy, on abase of aluminum, sold through S. M. GERZAT, at a pressure of 24 bar. Inthese mixtures, the initial concentration of nitrogen monoxide was setat 20 ppm. The stability of the concentration in terms of NO was studiedfor 3 bottles kept at ambient temperature over a period of 16 months.

The value of the NO concentration was measured by an analyzer withchemiluminescence in the range of 0 to 100 ppm, calibrated before eachmeasurement with the help of a standard NO/N₂ mixture at 90 ppm. Thechemiluminescence analyzer employed is the TOPAZE 2020 made by COSMA.

At the end of a period of 16 months, no decomposition of the nitrogenmonoxide in the NO/CO₂ mixtures, kept at ambient temperature, wasdetected. Indeed, the only fluctuations measured in the value of theconcentration of NO remain below the precision of the analysis.

These results confirm the stability of the medication compounds of theinvention.

EXAMPLE 2

This example is intended to demonstrate the effectiveness of the NO/CO₂compound of the invention, administered by way of intra-peritonealinsufflation, in the struggle against the hypoperfusion of the abdominalorgans and, in particular, the kidneys.

8 pigs, weighing approximately 25 to 30 kg, were anesthetized byintramuscular injection of ketamine (20 mg/kg) and mizadolam (0.1mg/kg).

After intubation, the anesthesia was maintained by injection of fentanyl(5 μg/kg/h) and pancuronium (0.5 mg/kg/h), and by inhalation of amixture of desflurane (5%), oxygen (50%) and nitrogen protoxide (45%).

We adjust the mechanical ventilation to maintain a partialremote-expiratory pressure of CO₂ which is less than 40 mm Hg.

Doppler® type detectors are implanted on the renal artery to measure thediameter of the arterial blood vessel and the speed of the blood so asto evaluate the average kidney blood flow.

In addition, a urinary probe is installed in the urethra to measure theurine flow.

The 8 pigs were divided into two groups of 4 pigs each. These 2 groupsof 4 pigs underwent intra-peritoneal insufflation for 2 hours, and at apressure of 15 mm Hg, consisting of the following:

gaseous CO₂ for group 1;

a gaseous mixture of NO/CO₂ (NO dose equal to 20 ppm) for group 2.

We observe a drop in the blood flow and the diuresis in the 2 groups ofpigs, as of the start of insufflation. However, the drop is less forgroup 2 (NO/CO₂ insufflated). In effect, after insufflation, the bloodand diuresis flow figures obtained for group 2 are 20% to 30% higherthan those obtained for group 1.

The gaseous compound of NO/CO₂ of the invention makes it possible toeffectively fight against the hypoperfusions of the abdominal organswhen it is administered intra-abdominally, that is to say,extra-peritoneally or intra-peritoneally, thus, in particular,permitting an increase in the blood flow on the level of the abdominalorgans.

We claim:
 1. A method for the treatment or prevention of hypoperfusionsof abdominal organs comprising administering to a patient in needthereof an effective amount of a gaseous medication comprising nitrogenmonoxide and carbon dioxide; wherein said gaseous medication isadministered by the intra-abdominal route.
 2. The method of claim 1,wherein said gaseous medication further comprises at least one gasselected from the group consisting of xenon, krypton, nitrogen protoxideand a combination thereof.
 3. The method of claim 1, wherein saidnitrogen monoxide is present in said gaseous medication in aconcentration of between 1 and 100 ppm.
 4. The method of claim 1,wherein said nitrogen monoxide is present in said gaseous medication ina concentration between 15 and 30 ppm.
 5. The method of claim 1, whereinsaid intra-abdominal route of administration is selected from the groupconsisting of the intra-peritoneal route and the extra-peritoneal route.